This invention relates to dry toner dispensing apparatus for use in electrostatic and the like copying machines.
Toner dispensers which are employed in electrostatic type copying machines are provided to supply toner automatically, to the developer mixture of carrier and toner provided in the copying machine developer apparatus. The addition of toner from the dispenser must be such that the ratio of carrier and toner is properly maintained to ensure that ample toner will be applied from the developer apparatus to the latent image on a photoconductive member being developed, regardless of copy demand. This in fact is not an easy task since the amount of toner particles in a developer mixture is sometimes as small as one or two percent. Furthermore, the toner particles are extremely small in size and have a low specific gravity. Also the toner particles are sensitive to heat, pressure, friction and moisture which can cause packing and fusing of the particles prior to dispensing.
Many types of dry toner dispensers are available for use with developer apparatus in copying machines, but few appear to be capable of providing sufficient variation in the quantity of toner dispensed to accommodate varying copy demands. One prior art toner dispenser includes a hopper having an opening at the bottom for feeding toner particles into a developer apparatus. The dispensing of the toner particles is accomplished by using a metering device, such as a roller, mounted in the opening and arranged to be rotated to permit toner to be dispensed by gravity into the developer apparatus. The last-mentioned toner dispenser, while being suited for some copy demands, is not sufficiently regulatable to dispense precise amounts of toner into the developer apparatus for varying copy demands.